Need some help with a command trac 4x4

Hello Everyone, Today I looked at a 2000 cherokee sport. Looked to be in excellant mech and visual condition. Drove the car, felt great, tight. Then, I engaged the 4x4. Here is where I need some help from you expericenced cherokee owners. I am new to the jeep famliy. I'm used to hitting an electrc botton hand really not noticing a driving difference. When I engaged the 4x4 I noticed first a sqeaking noise / humming coming from the shift location. Also I was able to tell something was different,ie traction was noticeable. And then when I turned I heard the dreaded clicking sound.
The clicking sound only happened once on the first turn. From that point on I did not hear the click sound. The owner told me that the vehicle has not been driven much over the past year. (squekie rubber noise). So here is my question, is the command trac system a more bare bones / rough kind of setup? I had owned a 98 grand cherokee with quadra drive so, it was alway on.

I have command trac 4x4 in my 93 cherokee, and when I pull my shifter to 4H, I don't notice any difference. When you turn on dry, non slippery sufaces though it will chirp the tire a little. If it hasn't been driven that much maybe it needs new U-joints. When the U-joint goes you will hear a high pitched squeel at low speeds with the windows down. I would check the drive shafts for more than usual play, and the front axles. I would also have them jack up the front end and shift the tire from top to bottom to see if maybe you have a bad hub or ball joint.

Quadra-Drive, as well as most all-wheel-drive traction systems, has a center differential that dynamically splits power between the front and rear axles. This is why you can make sharp turns when all four (well, two in reality) wheels are powered -- the diff inside the transfer case is allowing the front and rear axles to operate at different rotational speeds.

Command-Trac and traditional "4x4" systems simply employ a mechanism that connects the front and rear axles when engaged. The NP231 in Cherokees uses a chain for this purpose, while other (usually stronger) transfer cases have a gear system, similar to a manual transmission. Because there is no fluid coupling between outputs, both driveshafts turn at the same speed relative to each other. When making a turn, something has to give. This is why your tires may chirp on paved surfaces in 4WD. You can see why it's not a good idea to use 4WD on surfaces with high traction; it puts a lot more stress on the mechanical components and can lead to premature failure.

The humming (even "whining") noise you hear from the transmission tunnel may just be the transfer case itself. Both my YJ and XJ have a distinctive tone while driving in 4WD. This is even with a rebuilt transfer case in the XJ with brand new bearings.

Like andrew2516 mentioned, examine the U-joints as much as you can, look for worn ball joints, and definitely check for bad wheel bearings. Don't forget the U-joints in the steering mechanism of the front axle. Even if a joint is bad, they only cost about $15. Now, putting them in is another story... .

Command-Trac is a part-time system. Your Quadra-Drive was a full-time system. You should not use a Command-Trac in 4WD on dry pavement because it can cause the transfer case to bind up internally and self-destruct. I'm guessing you tested it on dry pavement.

The whirring noise you heard is typical. 4WD is driven by a chain, much like a flat-style timing chain, and in 4WD mode it's normal to hear it.

Yes, the Command-Trac is more of a "bare bones" system than Quadra-Drive.

Command-Trac = NP231 = do NOT drive in 4x4 on high-traction surfaces such as dry roads.
Selec-Trac = NP242 = Allowable to drive in 4wd on high-traction surfaces without endangering the structural integrity of the transfer case.

Thank for all the advice, I was driving the jeep out of a parking garage so the pavement was dry. Thanks agaiin.

yes, you may have damaged the 4x4 system if you took turns with it engaged on pavement, that is about the worst thing you can do.

the fact that the owner had no clue about this and did not stop you probably indicates that they also may have damaged the system prior to your test drive.

consider this a lesson learned and be happy you don't have an owner taking you to small claims court!

copbait said:

yes, you may have damaged the 4x4 system if you took turns with it engaged on pavement, that is about the worst thing you can do.

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Driving like this a few times isn't going to destroy the transfer case. They're a lot stouter than you might think. I've done more than my fair share of driving on dry pavement (testing purposes) with no ill effects on either the XJ or YJ. A rotational difference only happens when the vehicle's making a turn, anyway.

Heck, it took me a year of heavy four-wheeling to figure out that the previous owner of my YJ had different gears between the front and rear axles. That thing made all kinds of weird noises in 4WD... but I think the bucking back-and-forth was the funniest. It's been two years since I regeared them similarly, without rebuilding the t-case, and I haven't had any problems.

iroc86 said:

Driving like this a few times isn't going to destroy the transfer case. They're a lot stouter than you might think. I've done more than my fair share of driving on dry pavement (testing purposes) with no ill effects on either the XJ or YJ. A rotational difference only happens when the vehicle's making a turn, anyway.

Heck, it took me a year of heavy four-wheeling to figure out that the previous owner of my YJ had different gears between the front and rear axles. That thing made all kinds of weird noises in 4WD... but I think the bucking back-and-forth was the funniest. It's been two years since I regeared them similarly, without rebuilding the t-case, and I haven't had any problems.

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You may get lucky and not break anything, but at the very least there will be some serious wear and tear and life reduction. Why would you even want to take the risk though? If you really need to test I'm sure it can't be that hard to find a dirt or gravel road, and most dealers that sell 4x4 vehicles usually have a designated area for that kind of testing.

I'm not trying to be overly dramatic, I just don't think it's anything to press your luck on unless it is truly necessary, which I can't really see ever being the case.

copbait said:

You may get lucky and not break anything, but at the very least there will be some serious wear and tear and life reduction..

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And yet folkes will drive for hours on slick rock, with more traction than pavement, and not think twice about it.

Good idea? - No
End of world? - No

Bottom line - Don't worry about it.

Rev

Rev Den said:

And yet folkes will drive for hours on slick rock, with more traction than pavement, and not think twice about it.

Good idea? - No
End of world? - No

Bottom line - Don't worry about it.

Rev

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I was specifically talking about TURNING on dry pavement (or any high traction surface for that matter), please re-read my original reply for clarification.

copbait said:

I'm not trying to be overly dramatic, I just don't think it's anything to press your luck on unless it is truly necessary, which I can't really see ever being the case.

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You're absolutely right... and turning is the killer, which you mentioned. I'd never imagine driving around in 4WD on dry pavement just for fun, but once or twice isn't going to hurt it. There are tons of 4x4s out there without a center diff, with most of the owners clueless about proper usage of a "traditional" transfer case. They gotta build some idiotproofing into these things . U-joints would probably be the first thing to fail, anyway.

Not trying to disagree or anything; just accounting from my own experience.